He's never advised me to go that route, but then our goal may have been different as well. My first custom reamer I was hell bent to get a tight one, but was talked out of it by a couple BR smiths before even talking to Dave and that advice has stuck with me So far served me well but the next one I may have wished to go tight!

I think there may be some confusion here? As in case design vs reamer specs and clearance.

What I am talking about is the case itself. When I was first considering the 270 Montana (and others), I was thinking of blowing the parent case web out from the spec'd .445 to .450 (The actual virgin brass measurement is about .442) I called Dave to ask him his opinion on that and he recommended that I NOT blow the web out at all and that infact a lot of guys decrease the web diameter to help keep the primer pockets tight. This is exactly what he told me. So I decided to go with the actual new virgin brass dimensions of .442 This is what the Hornady custom dies are spec'd to. The sized case will be .442 at the web.

Now, as for the reamer, I was leaning to 2 thou clearance (.444) and he strongly recommended I go with 3 thou clearance (.445) and that is what the reamer print reflects at this moment. He also said to go with 4 thou clearance at the shoulder because of the shoulders radius which is over my head, but he's the expert and I went with his recommendation.

__________________
- Mark

You will never know how much it has cost my generation to preserve your freedom. I hope you make good use of it.
~ John Quincy Adams

Wow! that is plenty of room to improve. Like I previously stated though, he will get quite a bit of length shrinkage.........rich

Rich, how much shrinkage do you get when fire forming the 6.5 Sherman?

Mud, you might want to rethink your OAL and neck length. Your drawing shows an OAL that is .007 longer than the parent spec. Most new brass usaully comes about .005-.010 shorter than spec'd. My Norma 300 WSM brass is .010 shorter than spec and with the 35* shoulder, it does not grow.

When you fire form, blowing out the shoulder is probably going to "pull" the neck downward. How much, I don't know. But all in all, you could end up with a neck that might be 30-40 thou shorter than planned and probably at least 20 thou less. I would research this and Kiff can probably give good advise here as well.

__________________
- Mark

You will never know how much it has cost my generation to preserve your freedom. I hope you make good use of it.
~ John Quincy Adams

Rich, how much shrinkage do you get when fire forming the 6.5 Sherman?

Mud, you might want to rethink your OAL and neck length. Your drawing shows an OAL that is .007 longer than the parent spec. Most new brass usaully comes about .005-.010 shorter than spec'd. My Norma 300 WSM brass is .010 shorter than spec and with the 35* shoulder, it does not grow.

When you fire form, blowing out the shoulder is probably going to "pull" the neck downward. How much, I don't know. But all in all, you could end up with a neck that might be 30-40 thou shorter than planned and probably at least 20 thou less. I would research this and Kiff can probably give good advise here as well.

The shrinkage varies from brand and lot but it averages around .015". I agree that he should change his oal quite a bit. I'm thinking around .020" shrinkage with that design?......Rich
Also, on the previous post, only .002" clearance on the web will cause serious extraction problems on a .530" size case head.....

Rich, how much shrinkage do you get when fire forming the 6.5 Sherman?

Mud, you might want to rethink your OAL and neck length. Your drawing shows an OAL that is .007 longer than the parent spec. Most new brass usaully comes about .005-.010 shorter than spec'd. My Norma 300 WSM brass is .010 shorter than spec and with the 35* shoulder, it does not grow.

When you fire form, blowing out the shoulder is probably going to "pull" the neck downward. How much, I don't know. But all in all, you could end up with a neck that might be 30-40 thou shorter than planned and probably at least 20 thou less. I would research this and Kiff can probably give good advise here as well.

According to RCBS Cartridge Designer, the OAL is the exact same (2.6570")...

__________________
"I'm just a peckerwood who lives in the hills with too many guns..." - Bob Lee Swagger